The present invention relates to a system for checking the inflation pressure of the tyre, to a tyre wheel and to an inner tube comprising devices for checking the inflation pressure of the tyre.
The wheel is the component providing a connection between vehicle and road; it performs the function of providing support of the pneumatic type to the vehicle and to its load and of ensuring, by means of the tyre, an adequate road-holding performance. Support of the vehicle is provided by the volume of pressurized air contained inside the wheel.
The tyre comprises an internally hollow toroidal structure formed by a plurality of components and, primarily, by a textile or metallic carcass ply having two beads each defined along an internal circumferential edge of the carcass for securing the tyre to the corresponding support rim. It also comprises at least one pair of annular reinforcing coresxe2x80x94usually called xe2x80x9cbead wiresxe2x80x9dxe2x80x94which are circumferentially unextendable and inserted in said beads (usually at least one bead wire per bead).
The carcass ply includes a support structure which comprises textile or metal cords, axially extends from one bead to the other so as to form a toroidal structure and has its end edges each associated with a corresponding bead wire.
In tyres of the so-called radial type, the abovementioned cords lie substantially in planes containing the axis of rotation of the tyre.
On the periphery of this carcass there is arranged an annular overstructure, known as a belt structure, which is normally composed of one or more strips of rubberized fabric which are superimposed on each other so as to define a so-called xe2x80x9cbelt packxe2x80x9d, and a tread band made of elastomer material, wound around the belt pack and moulded with a raized design for the rolling contact of the tyre on the road. Moreover, the carcass is provided, in axially opposite lateral positions, with two sidewalls which are made of elastomer material and each extends in the radial direction outwards from the external edge of the associated bead.
In tyres of the so-called tubeless type, i.e. such as not to require the use of an inner tube during operation, the inner surface of the carcass is normally lined with a so-called liner, namely one or more layers of elastomer material which are impermeable to air. Finally, the carcass may comprise other known components, i.e. edgings, fillets and fillings in accordance with the specific tyre design.
A tyre wheel for vehicles comprises a tyre defining a toroidal cavity and mounted on a corresponding rim, which has a bottom surface provided with a central well and two bead seats on which the tyre beads rest in abutment and which are each axially delimited between a radial end surface (shoulder) in an axially external position and an opposing, axially internal, annular projection for fixing the bead on the corresponding seat.
In a tyre of the tubeless type the pressurized air is contained between the tyre and the support rim. The liner layer arranged on the internal surface of the tyre is designed to keep the pressurized air inside the latter. This tyre is usually inflated by means of an inflation valve which is usually arranged on the neck of said rim.
A tyre of this type is described for example in patent application Ser. No. EP928680.
A further solution for maintaining the supporting capacity of the tyre consists in the use of an inner tube which is inserted between tyre and rim and inflated with pressurized air introduced into the inner tube by means of an inflation valve projecting outside the wheel.
The inner tube, which is inserted between tyre and rim, comprises an expandable torus-shaped tubular body which is generally made of elastomer material and is inflatable by means of an associated inflation valve.
The valve for inflating the inner tube usually comprises a base for connection to the inner tube and a cylindrical casing (stem) which is fixed to the base and which has arranged inside it the activation mechanism for the inflation and deflation operations.
A tyre which is not correctly inflated reduces the efficiency of the vehicle; it produces in particular an increase in the fuel consumption, a deterioration in the manoeuvrability characteristics, and a greater wear of the tyre, to mention only the main drawbacks.
It is therefore of the utmost importance to be able to monitor continuously the trend of the pressure in the tyres of the vehicle.
The U.S. Pat. No. 5,540,092 describes a system for monitoring the pressure in a tyre, comprising a pressure detection unit and a unit for transmitting a coded signal to the vehicle fitted with the tyre. The transmitting unit may be mounted inside or outside the tyre. The transfer of this coded signal occurs by means of inductive coupling between the transmission unit and a fixed antenna. A battery supplies power to this transmission unit.
The U.S. Pat. No. 5,900,808 describes a system for detecting low pressure in a tyre, comprising low-pressure sensor means supplied by a battery and a radiofrequency transmitter for transmitting the signal generated by these sensor means to a receiver. The system also comprises switching means designed to enable energization of the transmitter when the sensor means signal a low-pressure condition within the tyre. The life of the battery is preserved since the transmitter is energized only when it is required to transmit a signal to the receiver.
The U.S. Pat. No. 5,562,787 describes a method for monitoring the conditions of a vehicle tyre, for example the pressure and the temperature of the air inside the tyre. The method uses a programmable self-energized device which is mounted on the internal surface of the tyre or inserted in the wall of the support rim of said tyre. The device comprises a power supply source which may be activated or deactivated using a switching device, a sensor designed to monitor the abovementioned information, an integrated circuit, an amplifier and an antenna.
A transmitter-receiver, which is located on the vehicle or in a remote position, interrogates the programmable self-energized device which responds with a radiofrequency signal which contains the required information. The programmable self-energized device is activated by said remote transmitter-receiver which operates the switching device which causes the power supply source to be activated.
The Applicants have noted that, in the present art, the devices for measuring physical parameters such as, for example, pressure and temperature, of a tyre wheel and the devices for transmitting the values of said parameters are energized also during non-operative conditions, for example when the vehicle is at a standstill, or activated by means of a command which is generated outside the wheel and on which the decision to provide information on the state of said tyre wheel depends.
The Applicants have considered the problem of providing a system for monitoring the operating conditions of a tyre wheel, for example the pressure and temperature of the air inside the tyre itself, in which the detection of these conditions is performed during travel of the vehicle without the need for an activating command from outside said tyre wheel.
The Applicants have found that, by using a movement sensor arranged inside the tyre wheel and able to detect the movement of said wheel, it is possible to perform measurement only during the desired operating conditions.
In particular the movement sensor enables energization of a sensor which is arranged inside the wheel, on the rim supporting said tyre or inside the inner tube, and which measures said operating conditions.
A first aspect of the present invention relates to a system for checking at least one status parameter of a tyre for a motor vehicle comprising:
at least one tyre wheel comprising a tyre mounted on a mounting rim,
a device for measuring said at least one status parameter associated with said wheel,
a transmission device designed to transmit a signal indicating the value measured by said measuring device,
a receiving device designed to receive said signal indicating the value measured by said measuring device,
characterized in that it comprises a sensor for sensing the movement of said wheel, designed to enable energization of said transmission device when said wheel is moving. In particular, said transmission device is inserted in a bush fixed in the wall of said inner tube.
Preferably, said measuring device is inserted in said mounting rim.
Alternatively, said measuring device is associated with an inner tube inserted in said wheel. In particular, said transmission device is inserted in a wall of said inner tube in a radially internal position.
Preferably, said movement sensor is an accelerometric switch.
Preferably, said measuring device and said movement sensor are housed in the same container.
Preferably, said device for measuring at least one status parameter of a tyre is a pressure sensor.
Preferably, said device for measuring at least one status parameter of a tyre is a temperature sensor.
In particular, said transmission device comprises a power supply battery, a device for measuring the voltage of said battery and transmits the value of the measured voltage by means of a radiofrequency signal.
The system further comprises a device for displaying said signal indicating the value measured by said measuring device.
Preferably the inner tube has at least two compartments which are separate from each other and each provided with said measuring device.
A further aspect of the present invention relates to a tyre wheel for vehicles comprising:
a tyre mounted on a corresponding mounting rim,
a device for measuring at least one status parameter of said tyre associated with said wheel,
a transmission device designed to transmit a signal indicating the value measured by said measuring device,
characterized in that it comprises a sensor for sensing the movement of said wheel, designed to enable energization of said transmission device when said wheel is moving.
Preferably, said measuring device is inserted in said mounting rim.
Alternatively, said measuring device is associated with an inner tube inserted in said wheel.
Preferably, said movement sensor is an accelerometric switch.
Preferably, said device for measuring at least one status parameter of a tyre is a pressure sensor.
Alternatively, said device for measuring at least one status parameter of a tyre is a temperature sensor.
Preferably, said transmission device, said measuring device and said movement sensor are housed in the same container.
A further aspect of the present invention relates to a sensor for measuring at least one status parameter of a tyre wheel for a motor vehicle, said wheel comprising a tyre mounted on a mounting rim, comprising:
a device for measuring at least one status parameter of said tyre,
a transmission device designed to transmit a signal indicating the value measured by said measuring device,
characterized in that it comprises a sensor for sensing the movement of said wheel, designed to enable energization of said transmission device when said wheel is moving.
Preferably, said sensor is inserted in said mounting rim.
Alternatively, said sensor is associated with an inner tube inserted in said wheel.
In particular, said sensor is inserted from the outside into said mounting rim.
Preferably, said transmission device, said measuring device and said movement sensor are housed in the same container.
Further characteristic features and advantages will appear more clearly from the detailed description of a preferred, but not exclusive embodiment of the different aspects of the present invention.